1. Field of Invention
The present invention relates to a signal transmitting method, and more particularly to a wireless audio signal and control signal device and method thereof, which enhances the voice quality during the wireless signal transmission while being cost effective.
2. Description of Related Arts
The wireless transmission of voice signals is nowadays popular among the audio advices, such as the intercoms, the wireless microphones. But these apparatuses are limited to transmit analog signals. With the improvement of modern technology, the function of transmitting both voice analog signals and digital control signals controlling over the designated device are realized. In order to fulfill the stated functionality, the contemporary transmission methodology is realized with the process of firstly digitizing the analog voice signals by the analog-digital conversion (ADC), and then compressing the digitized voice signals to thereafter combine with the digital control signals, whereupon the mixture of digitized voice signals and the digital control signals are in order high-frequency modulated, high-frequency amplified, then high-frequency transmitted, referring to FIG. 1. To use low-bit rate to transmit the voice signals will suffer the poor quality of voice signals recovery due to the limitation of bandwidth. If the transmission of 20 KHz voice signals is needed, according to the sampling theory the minimum 40 KHz sampling rate is required for full recovery of the original voice signals without suffering the sampling error or sampling loss, with a 16-bit analog-digital conversion, the data storage of 640K bit per second is necessary. Even the data compression is capable of reduce the quantity of each transmission, the compression also brings effect on the loss of quality of each data and consequently limit the compression ratio. The common digital wireless phone with low-bit rate transmission which uses a 3.4 KHz bandwidth, while the frequency of human voice during conversation is in the range from 11 Hz to 8 KHz, only sustains a voice recognition standard. But the high-bit rate transmission is inevitable of using the high cost integrated circuit designated for high speed coding and decoding.
Therefore, the balance between desirable voice quality and reasonable unit cost is hard to achieve.